In the Victoria Longitudinal Study (VLS), we conduct a series of cross-sectional and longitudinal studies pertaining to the description and explanation of changes in cognitive performance in late adulthood. The research derives from the perspective that the magnitude and rate of late-life changes in memory performance depend substantially on individual differences in such underlying factors as (a) cognitive ability and resource components, (b) metacognitive and compensatory knowledge and implementation, (c) selected health, biomedical, sensory, neuropsychological, and physiological conditions, and (d) lifestyle, activity, and demographic background indicators. The principal objective is to continue an ongoing large-scale longitudinal investigation, thereby enhancing a unique and increasingly rich data set on human aging.The VLS is designed as a longitudinal sequential study. Three independent samples of 55-85-year old adults are recruited at six-year intervals. Each sample is re-tested at three-year longitudinal intervals. To date, Sample 1 (original n=484; average return rate over 70%) has been tested five times over 12 years (start years 1986, 1989, 1992, 1995, 1999). The sixth wave occurs in 2002. Sample 2 (original n=530; average return rate over 80%) has been tested three times over six years (start years 1993, 1996, 1999). The fourth (late 2002) and fifth waves (2005) occur in this research period. Sample 3 (expected n=530) is presently being tested (current n=300). The second wave begins in 2004. Several comparison samples have been developed in recent years. Approximately 10 hours of data are collected per participant at each occasion. In sum, the proposed research is designed to examine the extent and trajectories of aging-related cognitive and memory changes, as influenced by (a) patterns of differential decline in theoretically derived classes of influencing cognitive components, and (b) conditions representing selected physiological, health, and lifestyle characteristics.